A woman injured in a rocket attack is transferred from a military ambulance to a civilian ambulance near Nahal Oz, Israel. Israel resumed attacks on Hamas in the Gaza Strip in response to rocket and mortar fire.

Efforts by the United Nations to get Israel and Hamas to extend a "humanitarian pause" in fighting in the Gaza Strip collapsed on Sunday as Israeli forces resumed bombardments and shelling in response to renewed rocket and mortar fire from the Palestinian territory.

Israel had declared a 24-hour cease-fire at midnight Saturday, but said it resumed attacks because of violations by Hamas.

The Islamist group declared its own 24-hour cease-fire at 2 p.m. local time on Sunday, citing the hardships of Palestinian civilians and the approaching Muslim holiday of Eid al-Fitr, but Israel rejected it.

After truce talks failed, President Obama intervened to press Israeli Prime Minister Benjamin Netanyahu to agree to an immediate cease-fire, calling it a "strategic imperative," the White House said. The drive to halt fighting continued early Monday when the U.N. Security Council issued a statement calling for a cease-fire.

Diplomatic efforts to secure a truce appear to be mired in disagreements over the terms. There were signs of dissatisfaction in Israel with the mediation efforts of U.S. Secretary of State John Kerry.

The war so far has killed more than 1,000 Palestinians and wounded more than 6,000, according to Gaza health officials. The U.N. said three-quarters of the dead in Gaza are civilians, including more than 200 children. About 200,000 Palestinians have been displaced by the fighting, and most are sheltered in U.N. schools.

Two Israeli civilians and a Thai laborer have been killed in rocket strikes against Israel, and 43 Israeli soldiers have been killed in ground combat.

The absence of a trusted mediator has hobbled diplomatic efforts to halt the Israeli offensive, which began July 8 with bombardments from land, sea and air, followed 10 days later by a ground push into Hamas-controlled Gaza.

The diplomacy has also been complicated by regional tensions between Egypt and the Palestinian Authority on the one side, and Hamas and its allies, Turkey and Qatar, on the other. Hamas rejected an initial cease-fire proposal put forward by Egypt, reflecting its distrust of Egyptian President Abdel Fattah el-Sissi, who is hostile to the Islamist group and its parent organization, the Muslim Brotherhood.

Kerry's attempts to broker a deal have foundered over Israeli dissatisfaction with the terms of his latest proposal for a seven-day cease-fire. Israeli officials described it as heavily weighted in favor of Hamas demands.